The impact of increased wind power on the steady state and dynamic behavior of the Ethiopian power system is the main focus of this thesis. The integration of wind power to the existing grid with conventional generators introduces new set of challenges regarding system security and operational planning, the main cause of the difference arising from the uncertainty of the primary source of energy and the response time following a disturbance.
For incorporating wind turbine models into the overall dynamic model of the system and investigating the effect of wind on the dynamic behavior of the wind first models of wind turbine components were put together by reviewing the current state of the art in wind turbine modeling and control concepts. The theoretical insight thus gained was applied to the Ethiopian power system as a case study. Since the models of the installed turbines were either not available or incomplete, an alternative modeling approach based on generic models was adopted.
The generic model, in addition to obviating the need for technology or manufacturer specific models, reduces the complexity the dynamic model. Using this procedure, generic dynamic models for wind farm in the system were developed. The capability of dynamic models to reproduce the dynamic response of the system has been verified by comparing simulation results obtained with a detailed and generic wind farm model. It could be shown that the generic wind turbine model is simple, but accurate enough to represent any wind turbine types or entire wind farms for power system stability analysis.
The next task was the study of the effect of increased wind power level on the general behavior of the Ethiopian system. It is observed that overall the impact of wind turbines on the operational indices of the system was –as could be expected- more pronounced in the vicinity of the wind farm. But the power angle oscillation following a disturbance was observed across the whole system. Further, as a result of the decoupling of the mechanical rotor of the wind turbine grid and the reduction of the overall system inertia as a result, the oscillation of generators becomes more pronounced as more and more conventional generators are replaced by wind turbines. It is observed that the critical fault clearing time slowly decrease with an increase in wind power level indicating insignificant degradation of system security in the system.
In the subsequent stage investigations were performed regarding the small signal (dynamic) stability of the system as the share of wind increases by computing the eigenvalue spectrum of the system. The following general conclusions can be deduced from the analysis:
• The effect of replacing conventional generators by wind turbines as regards the small signal behavior of the system as reflected by the damping behavior of the dominant Beles hydropower plant unit (BEL) can be characterized as minor.
• The same conclusion can be reached regarding load changes in steady state. The impact of system load levels with no wind power and with maximum wind generation on the damping performance of the system suggests that the damping performance of the system is not significantly affected either by the level of system load or the amount of wind generation.
• On the basis of these investigations, it can be concluded that the integration of large scale wind generation does not appear to affect the overall small signal stability of the Ethiopian power system.
Finally, with the increasing level of penetration of wind, the need for establishing a standard operating practice such as grid code for wind turbines becomes obvious. Based on the detailed study performed in this research and the experiences of other countries a new Ethiopian wind grid code has been proposed

Rights

Use and reproduction:

Export

DuEPublico
is the institutional repository of the University of Duisburg-Essen.
DuEPublico is driven by the university library and
based on the repository framework MyCoRe and additional Open Source components.
Find out more...